Hi, I'm using Ubuntu 10.04 with a recent gnuradio-next branch and the UHD driver on USRP2/WBX boards. In an outdoor setup I have two receiving nodes about 40m away from each other and from the transmitter. The transmitter is a PC with two USRP2s connected with a MIMO cable. It is sending two different PN sequences every 120ms on both interfaces at the same time. I correlate the known sequences at the receivers to measure the channel gain. The results can be seen here (x-axis is the packet number, y is the absolute gain):
http://cs.ucsb.edu/~veljko/downloads/channel_gains_outdoor.jpg The gain seems to be varying with around 2 Hz frequency. Since the setup is static and the tx/rx gain is not modified during the course of the experiment I'm almost certain that the artefact comes from the system rather than from the environment. Does anyone have a good explanation for this? Perhaps there is some sort of a gain control in the USRP2 that I'm not aware of? I got similar behavior when I tried the same experiment indoors. Thanks, Veljko _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
